JPH0381267B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to current producing batteries, and more particularly to such batteries that utilize certain cathode active materials consisting of or derived from ammonium, molybdenum, chalcogenide compounds.

In recent years there has been considerable interest in the development of high energy density batteries for chemical batteries. An example of a system that has been developed is a high energy density chemical cell that utilizes a transition metal chalcogenide intercalation compound as the cathode active material and uses an alkali metal anode, as described in US Pat. No. 4,009,052. U.S. Pat. No. 3,915,740 discloses MoS _x (but 2
x3) and US Pat. No. 3,864,167 describes certain fibrous transition metal trichalcogenides as cathode active materials. U.S. Pat. No. 3,655,585 describes a cell that utilizes vanadium pentoxide, made by thermal decomposition of ammonium vanadate, as the cathode active material.

U.S. Patent No. 3898096, No. 3925098, No.
No. 4003753 has an alkali metal anode, e.g. lithium, a molten salt electrolyte, Cu and Fe
sulfides, sulfides and oxides of Ni, molybdenum sulfide, and potassium thiomolybdate
A chemical cell is described having a cathode containing a chalcogenide such as K ₂ MoS ₄ .

However, despite the considerable variety of recently developed high energy density chemical cell systems, it is believed that the particular cells of the present invention containing ammonium, molybdenum, and chalcogenides have not heretofore been identified.

The present invention provides (a) an anode having as an anode active material one or more metals selected from the group consisting of group A metals, group B metals, group A metals, and group B metals of the periodic table; (b) a cathode. As an active material, ( _i ) the _following formula (NH ₄ ) , x is a number of 2 and y is a number of about 4), (ii) one or more hydrogens are alkyl groups having from 1 to 20 carbon atoms and from 1 to 20 A compound of the above formula substituted with a group selected from alkylamine groups having a carbon atom, (iii) the following formula (NH ₃ -R-NH ₃ )MOZy (2) (where R is a methylene group or 2 to 20 is an amorphous decomposition product of one or more compounds selected from the group consisting of a polymethylene group having carbon atoms of The decomposition products are obtained by thermally or chemically decomposing them at temperatures between 50°C and 350°C, and when tested with an X-ray diffractometer, no sharp reflections are observed, and the sulfur metal ratio is (c) an electrolyte that is chemically inert to the anode and the cathode and that allows the movement of ions between the anode and the cathode.

As mentioned above, the current generating battery of the present invention is a battery that includes a specific anode, a functional electrolyte, and a cathode having as the cathode active material a compound derived from ammonium, molybdenum, or chalcogenide compounds.

In general, the anode used in the battery of the present invention includes a group A metal of the periodic table as its anode active material.
The battery contains one or more metals selected from the group consisting of group B metals, group A metals, and group B metals. Among these, it is desirable to use Group A metals known as alkali metals. An anode having a metal selected from the group consisting of lithium and sodium as an anode active material is preferred, and lithium is most preferred. Depending on the particular anode active material used, the anode active material can be contacted with other metal structures in the cells of the present invention. Therefore, for example, certain anode active materials are self-supporting;
It can also act as a current collector, while other anode active materials, such as lithium, can be contacted with other metal structures, such as nickel, copper or silver screens, which act as current collectors. This anode configuration is a matter of design depending on the particular anode active material used and is well known in the art.

The cathode used in _the battery of the present invention has the following cathode active material: ( _i ) The following formula (NH ₄ ) a chalcogen selected from the group consisting of a mixture, x
(ii) one or more hydrogens are an alkyl group having from 1 to 20 carbon atoms and y is a value from 1 to 20 carbon atoms. A compound of the above formula substituted with a group selected from alkylamine groups having atoms, (iii) the following formula (NH ₃ -R-NH ₃ )MOZ _y (2) (where R is a methylene group or 2 to 20 is an amorphous decomposition product of one or more compounds selected from the group consisting of a polymethylene group having carbon atoms of The decomposition products are obtained by thermally or chemically decomposing them at temperatures between 50°C and 350°C, and when tested with an X-ray diffractometer, no sharp reflections are observed, and the sulfur metal ratio is It is greater than 2.5 and less than 4.

As defined above, the variable Z represents a chalcogen selected from the group consisting of sulfur, selenium, sulfur-selenium mixtures, sulfur-oxygen mixtures, selenium-oxygen mixtures. Desirably, Z is selected from the group consisting of sulfur and selenium. Preferably chalcogen Z is sulfur.

The compound of formula (1) above is one in which one or more hydrogen atoms are substituted with a group selected from an alkyl group having 1 to 20 carbon atoms and an alkylamine group having 1 to 20 carbon atoms. including. Alkylamine group means an alkyl group having an _-NH2 substituent. Preferably, one of the compounds of formula (1)
One or more hydrogens are replaced with groups selected from alkyl groups having 1 to 12 carbon atoms. Preferably, this is an alkyl group having 1 to 4 carbon atoms and an alkylamine group having 1 to 4 carbon atoms.

In the compound of the above formula (2), R is a methylene group or 2-
It is a compound that is a polymethylene group with 20 carbon atoms. Desirably R is a methylene group or a polymethylene group having 2 to 12 carbon atoms. Preferably R is a methylene group or a polymethylene group having 2 to 4 carbon atoms.

Of all the compounds used as cathode active materials in the cells of the invention, preference is given to the decomposition products of the compounds of formula (1) above.

Among the compounds (i) to (iii) used in the present invention, there are the following.

(NH ₄ ) ₂ MoS ₄ (NH ₄ ) ₂ MoSe ₄ (NH ₄ ) ₂ MoS _{4-a Sea} (NH ₄ ) ₂ MoS _4-a O _a (NH ₃ CH ₃ ) ₂ MoS ₄ (NH ₃ CH _{3 ) ( NH3C2H5 ) MoS2O2 ( NH3C8H17 ) ( NH4 ) MoSe4 ( NH3C2H4NH3 ) 2MoS4 ( NH3C2H4NH3 ) _ 2} MoS ₄ (NH ₃ C ₁₀ H ₂₀ NH ₃ )MoSe ₄ (however, 4>a>0). It will be apparent to those skilled in the art that the various homologs and analogs described above are intended to be included herein as appropriate within the scope of the above formula. The cathode active material of the present invention is made as follows. For example, ammonium thiomolybdate or substituted ammonium thiomolybdate can be formed by passing sulfur vapor through a solution of ammonium molybdate or substituted ammonium molybdate, respectively. Amorphous decomposition products of ammonium, molybdenum, and chalcogen (substituted or unsubstituted) can be obtained at temperatures below about 350° C., which can be carried out by thermal decomposition or chemical decomposition. Therefore, from about 50℃ to 350℃
Heating ammonium, molybdenum, and chalcogens (substituted or unsubstituted) at temperatures up to very high temperatures results in at least some thermal decomposition of the compounds [e.g., TP Prasad et al. Chemistry (Journal of Inorganic and
Nuclear Chemistry) Volume 35, pp. 1895 et seq. (1973
2007)]. On the other hand, decomposition can be achieved by chemical reactions using acidic media, for example by treating the compound with an acid such as formic acid [see, for example, F.T. Egersten et al., Journal of
Physical Chemistry (Journal of
Physical Chemistry), Volume 63, pp. 1981 et seq. (1959
2007)]. Although formic acid was chosen as the acid medium for chemical decomposition in the examples below, it should be noted that other acids such as acetic acid, chloroacetic acid, benzoic acid, citric acid, hydrochloric acid, phosphoric acid, hydrobromic acid, sulfuric acid, etc. can be used. Should. In fact, any acid can be used to chemically decompose ammonium molybdenum chalcogen compounds to yield amorphous decomposition products, as long as sufficient acid is also used to maintain a pH in the range of about 2 to about 5.

When the decomposition products of ammonium thiomolybdate are formed by heat treatment or chemical treatment at temperatures below about 350°C, the sulfur metal ratio is greater than 2.5 and 4.
A product of generally amorphous structure is obtained which is:
On the other hand, when heated to a higher temperature, it changes to molybdenum disulfide. It has been surprisingly found that sulfide decomposition products obtained at temperatures below about 350°C yield chemical cells of significantly higher energy density than molybdenum disulfide obtained by pyrolysis at about 350°C (this is discussed below). This becomes clearer from Examples 7 and 8).

Cathode active materials of the above compounds that have been at least partially decomposed thermally or chemically are generally characterized by amorphousness and do not exhibit sharp reflections in X-ray diffractometer studies. Furthermore, platelets typical of disulfides as described in US Pat. No. 4,009,052 or fibers as typical of trisulfides as described in US Pat. No. 3,864,167 were not observed under scanning electron microscopy.

Advantageously, the cathode active material of the cell according to the invention can simply be hot pressed (in this case accompanied by at least partial thermal decomposition) into a cathode structure, but the thermal or chemical decomposition described above can be applied before construction of the cathode.
The cathode active material can be supported on structures such as carbon, copper, nickel, stainless copper, iron, etc.
Or it can be impregnated into the above substances. Advantageously, the cathode does not include a conductive diluent such as carbon within the cathode active material. A plastic binder such as polyfluoroethylene can also be used if desired.

The electrolyte used in the battery of the present invention is an electrolyte that is chemically inert to the anode and cathode and that allows the movement of ions between the anode and cathode. Generally, the choice of electrolyte is related to the anode active material used in the battery. Therefore, when the anode active material is a Group A metal, the electrolyte is most suitably non-aqueous. However, if the anode active material is selected from group B metals, for example,
Aqueous electrolytes can be used. When the preferred anode active materials selected from Group A metals are used in the cells of the present invention, the electrolyte can typically be a non-aqueous alkali metal salt-organic solvent electrolyte solution. These alkali metal salts are well known in the art and need not be listed here. However, such salts include lithium and sodium salts dissolved in organic solvents, such as inertly substituted and unsubstituted ethers, sulfones, organic sulfates, organic sulfites, organic nitrites, and organic nitro compounds. Contains a complex of A preferred electrolyte for use in cells containing lithium as the anode active material is an electrolyte containing dioxolane or a lithium perchlorate salt dissolved in a dioxolane-containing solution. One preferred electrolyte for cells containing sodium as the anode active material includes sodium triethylpyrrole boron dissolved in a cyclic ether containing solution. On the other hand, solid electrolytes such as β-alumina or halides, or molten salts can be used.

The decomposition product of the present invention is a chalcogenide having an interlayer structure, and exhibits a discharge reaction similar to that of chalcogenides.

There is therefore no substantial difference in the types of discharge reactions that can occur.

BACKGROUND ART Batteries in which a chalcogenide having an interlayer structure is used as a cathode active material and an alkali metal is used as an anode are known. During discharge of such a cell, lithium from the anode is intercalated into the cathode.

This is reversed when the battery is charging. That is,
Lithium from the chalcogenide is deposited on the anode.

The compounds of the present invention are all chalcogenides with an intercalated structure, and lithium becomes an intercalation of these intercalated materials.

When a battery is constructed with a chalcogenide having such an interlayer structure as a cathode and lithium as an anode, discharge occurs under load. This electrochemical reaction can be reversed.

The battery is thus charged by applying current to both electrodes and subsequently discharged by the load.

The cathode material undergoes substantially no discharge reaction. Then, charge is transferred and received. Batteries containing cathode materials are charged or discharged.

It should be noted that, as shown in the Examples, the battery containing the cathode active material of the present invention exhibits good reversibility and capacity.

The current generating cell of the present invention comprising the anode, cathode and electrolyte described above not only has a high energy density, but also can be charged and discharged repeatedly and can be easily manufactured on a large scale basis.

The present invention is illustrated by the following examples, but the present invention is not limited by the examples.

Example 1 Ammonium thiomolybdate was precipitated from an ammoniacal aqueous solution of ammonium molybdate by bubbling hydrogen sulfide into the aqueous solution. The precipitate was filtered under nitrogen. This was then mixed with 20% by weight of carbon and 10% by weight of polyfluoroethylene powder, first heated at room temperature and then heated to 300°C.
Pressed into an expanded stainless steel grate. The grid had approximately 2 cm ² of cathode active material. They then created a battery by surrounding the cathode screen with a polypropylene separator, which was then surrounded by pure lithium metal, which served as the anode.
The assembly was immersed in a 2 molar solution of lithium perchlorate in dioxolane. Then add a 1ma battery
discharged to a cutoff of 1.4 volts. Approximately 75% capacity was obtained between 1.75 and 2.0 volts.
The capacity at the first discharge was 1.78 kilocoulombs/g thiomolybdate. The battery was then cycled between 1.40 volts and 2.70 volts at least 20 times;
The battery showed high reversibility.

Example 2 A cell constructed and tested as in Example 1, except without the addition of carbon as a conductive diluent, exhibited similar electrochemical properties with a capacity of 1.73 kilocoulombs/g. Facile reversibility was also observed, indicating that there is no need to add conductive diluent to cells containing ammonium thiomolybdate as cathode active material.

Example 3 A cell was constructed as in Example 1, but the electrolyte was a 1 molar solution of sodium triethylpyrrole boron in dioxolane and the anode was sodium pressed into an expanded stainless steel screen. The initial open circuit voltage was 2.23 volts, and a capacity of 1.35 kilocoulombs/g thiomolybdate was obtained between 2.2 volts and 1.25 volts under discharge at 1 ma. More than 10 discharge cycles between 1.25 and 2.5 volts were obtained, indicating that this sodium cell is also highly reversible.

Example 4 Ammonium thiomolybdate formed as in Example 1 was analyzed at 10°C/min on a thermogravimetric analyzer.
Heated (under argon) to 1000°C. 19.2% of its initial weight is already lost by 250℃, and further
17.9% was lost at 370°C. The final reaction product was identified as molybdenum disulfide by X-ray analysis.

Example 5 Ammonium thiomolybdate, formed as in Example 1, was reacted in a Calvery reactor in 5 wt% dibenzothiophene in decalin at about 250°C.
The mixture was heated at 350° C. for 8 hours at a total pressure of 450 psi under dibenzothiophene and hydrogen. A cell was then constructed as in Example 2 using this material as the cathode active material. The first discharge capacity was found to be 0.24 kilocoulombs/g, which is substantially lower than the first three examples. This indicates that the active material of the present invention is a material that forms before the second weight loss found in Example 4.

Example 6 In this example, ammonium thiomolybdate was chemically decomposed before cathode construction. 200ml of 5% aqueous solution of ammonium thiomolybdate at 5℃
Dilute with 500ml of H ₂ O and adjust the pH by adding 5% formic acid.
was lowered to 3. It was then heated at 50°C for 0.5 hour, cooled, and left overnight. It was filtered, washed with 5% formic acid, and washed with 200 proof ethanol. Finally, it was dried in a vacuum oven, first at room temperature and then at 150° C. for 5 hours. This material had a BET surface area of 28.82 m ² /g. This compound was treated with butyllithium, and n-butyllithium was added per mole of molybdenum.
It was found that 4.5 moles were consumed. This high reactivity towards lithium indicates the usefulness of this molybdenum sulfur composition as a cathode active material.

Example 7 A battery was constructed as in Example 1, but using the molybdenum sulfur compound prepared in Example 6. This battery has 1.88 kilocoulombs per discharge in the first discharge.
It had an average discharge voltage of 1.85 volts. This value gives a theoretical energy density of 856 Watt hours/Kg (including lithium and cathode weight). The cell was cycled 18 times between 2.7 and 1.4 volts, where it demonstrated its high reversibility.

Example 8 A cell was constructed as in Example 7, but using the sodium electrolyte and sodium anode configuration used in Example 3. On the first discharge, this battery
It has a capacity of 1.53 kilocoulombs/g, then 2.5
volts and 1.25 volts more than four times, demonstrating the facile reversibility of this cathode material.

Example 9 Three samples of the precipitate formed as in Example 6 were heated in a preheated oven at 250°C, 400°C, and 600°C for 1 hour, respectively, and then cooled under a nitrogen atmosphere.

Measured by nitrogen adsorption, these three samples each had 18,
It had a BET surface area of 101.43 m ² /g. Example 1
The batteries are constructed as follows, and their capacities are respectively
It was found to be 1.80, 0.12, and 0.25 kilocoulombs/g. This shows that heating the sample to temperatures of 400° C. and above substantially reduces its capacity. These two samples had compositions corresponding to molybdenum disulfide. Furthermore, it can be seen from these three samples that high surface area, ie, small particle size, does not necessarily give high electrochemical activity.

Comparative Example 1 A battery was constructed as in Example 1, except that a single crystal of natural molybdenite (MoS ₂ ) weighing 150 mg was used as the cathode. The capacity of this battery is significantly lower, even when the discharge current is reduced to 0.1ma.
It was 0.006 kilocoulomb/g.

Comparative Example 2 5.0g of MoCl ₄ was added to ethyl acetate, then
1.9 g of Li ₂ S was added. The mixture was stirred for 2 days, filtered, then washed with methanol and ethyl acetate. This was done under nitrogen as described in pending US Application No. 641,424. A chemical cell was constructed from this molybdenum disulfide as in Example 1. The capacity of this cell was 0.49 kilocoulombs/g in the first discharge, which is considerably smaller than the cells of Examples 1, 3, 5, and 7. This clearly shows that even when produced at low temperatures, molybdenum disulfide does not have a capacity comparable to the materials of the present invention.

Example 10 Ethylenediamine thiomolybdate salt was prepared by adding 15 c.c. of ethylenediamine to 2 g of ammonium thiomolybdate. Then, 60 ml of methanol was added to obtain an orange precipitate. The precipitate was washed with hot methanol. Red ethylenediaminethiomolybdate was collected. This was then formed into a cathode as in Example 1 and discharged and charged more than 50 times, demonstrating its high reversibility.

Thiomolybdate dodecamine salt was prepared by reaction of 2.6 g of ammonium thiomolybdate and 4.4 g of dodecamine hydrochloride in 100 c.c. of methanol. The precipitated orange solid was formed into a cathode as in Example 1 and cycled over 40 times, demonstrating the high reversibility of this substituted ammonium thiomolybdate derived cathode.

Example 11 Ammonium thiomolybdate, formed as in Example 1, was reacted with n-butyllithium in hexane. When one equivalent of n-butyllithium was added, all the lithium was consumed by ammonium thiomolybdate. During the reaction, the molybdate changed from its characteristic red color to black.
When 5 equivalents of n-butyllithium were reacted with the molybdate, 2 equivalents of lithium were consumed.
This high reactivity towards lithium indicates the utility of this molybdenum sulfur composition as a cathode active material.

Claims (1)

[Scope of Claims] 1 (a) An anode having, as an anode active material, one or more metals selected from the group consisting of group A metals, group B metals, group A metals, and group B metals of the periodic table; (b) As the cathode active material, (i) the _{following formula} (NH ₄ ) (ii) one or more of the hydrogens is an alkyl group having from 1 to 20 carbon atoms; and a compound of formula (1) substituted with a group selected from alkylamine groups having 1 to 20 carbon atoms, (iii) a compound of the following formula (Ni ₃ -R-NH ₃ )MOZ _y (2) (wherein R is a methylene group or a polymethylene group having 2 to 20 carbon atoms, and Z and y are as defined above. , are amorphous decomposition products obtained by their thermal or chemical decomposition at temperatures between 50°C and 350°C, and exhibit sharp reflections when tested with an X-ray disfractometer. (c) is chemically inert to the anode and the cathode and allows the movement of ions between the anode and the cathode; A current generating battery comprising: an electrolyte;